Arc welding processes are well-known in the art and have been used for decades in production and other environments to join together two or more separate items or workpieces. Depending on the particular application, the part produced by the arc welding process may be more or less tolerant to variations in weld quality. For example, certain applications may be quite tolerant to variations in weld quality, with a wide range of weld defects still resulting in an acceptable part. Other applications, however, are very fault intolerant, with very few, if any, weld defects being tolerable in an acceptable part.
In many production welding applications, the procedures for producing a weld for a given application are usually established in advance. Accordingly, the rejection rate (i.e., the rate at which a defective weld will result in a defective part) is usually highly correlated with the established welding procedure. If a good procedure is established, then the rejection rate usually will be low. On the other hand, a fundamentally unsound welding procedure will result in a relatively high part rejection rate.
Even if a sound welding procedure is developed, the ultimate part rejection rate depends to a large extent on how closely the system operator follows the established welding procedure. Unfortunately, however, the sources of welding problems are many, and may include problems relating to poor welder maintenance (e.g., worn contact tip, dirty gas cup, poor grounding), problems with the weld fixtures (e.g., misalignment, fixture cleanliness), problems relating to the welding robot (e.g., reprogramming of welding robots without consideration of the effects on weld parameters), automation fallibility (e.g., poor fit-up), procurement of low quality consumables, such as filler wire, or the degradation of the welding equipment itself Therefore, the failure to properly follow the established welding procedure can quickly result in an increased part rejection rate.
Another problem that is often faced in a production environment is that the system operator usually does not take the time to ascertain the underlying problem causing the defective welds. Instead, the problem is often corrected by simply varying certain readily adjustable welding process parameters until the problem goes away. While such a procedure may result in a short-term fix, repeated corrections may eventually cause the welding process parameters to drift so far out of the parameter space defined by the initial procedure that weld defects become difficult to diagnose and eliminate, resulting in higher defect rates than would otherwise be encountered by adhering to sound welding practices.